In up to 10% of central serous chorioretinopathy (CSCR) cases, subretinal fluid may become persistent and require intervention such as nondestructive subthreshold laser therapy. An analysis of subthreshold yellow laser at 577 nm and accompanying software shows the treatment can resolve subretinal fluid and increase visual acuity. The Eye (London) study also shows that the decreased choroidal vascularity index (CVI) after subthreshold yellow laser treatment aids in the anatomical assessment of the choroid.
Researchers included 32 eyes of 32 patients with CSCR in this prospective study (mean age 48 years, 9 women, 23 men). All had been diagnosed at least 4 months prior, but were not previously treated. Participants chose whether to undergo laser treatment or continue with observation only, and so 2 groups formed; 14 patients treated with subthreshold and 18 individuals who did not receive laser. Baseline parameters of the 2 cohorts were similar, although after 3 months, comparison revealed differences in choroidal structures.
For laser-treated participants, specific parameters significantly improved after therapy; CVI (P =.046), total choroidal area (P =.024), and luminal area (P =.018). Further, CVI decreased compared with observed-only individuals (P =.011), as well as subfoveal fluid height (P =.003). Those who received subthreshold laser therapy experienced increases from baseline in choriocapillaris plexus (CCP) flow area (P =.002), and best corrected visual acuity (P <.001). Notably, investigators found that a positive correlation emerged between final BCVA and CVI (r=0.539, P =.01).
Subretinal fluid completely resolved in 10 eyes, 71.4% of the subthreshold-treated cohort, compared with 2 eyes, 11.1% of the observation group. The later set exhibited no significant changes from baseline to 3 months in choroidal parameters, subretinal fluid height, or BCVA. Also, for the 16 eyes who were observed only and did not show spontaneous fluid resolution, no significant changes from baseline occurred in subretinal fluid height and central macular thickness.
In previous research, CVI — the ratio of luminal area to total choroidal area — has been shown to increase in individuals with CSCR. The study authors suggest this index can be a valuable test of treatment response, rather than using choroidal thickness alone, because choroidal vessel dilation upon CSCR onset has been demonstrated, in addition to leaking from choriocapillaris to the stromal layer. “The pachychoroid spectrum disorders are affected by increased choroidal vascularity due to functional and structural changes of the choroid,” the investigators explain.
Advantages of subthreshold are capabilities to treat tissue near the fovea, and to retreat regions. In this study, laser power was titrated; starting with full-power 15 ms pulses placed away from the macula, down to 30% power to treat leaky or subretinal fluid-affected regions. With software that incorporates titration, treatment sites can be marked with what appears a point of greater autofluorescence in the RPE. Yellow laser also offers benefits involving absorption by both melanin and oxyhemoglobin, and reduced light scattering in the eye.
Laser treatment did not cause any adverse events. A short 3-month follow-up is a limitation of the analysis, as well as no machine randomization. Also, treatment comprised a unique laser wavelength and titration technique that differs from some other studies. Strengths comprise its 2-group design, and being first to examine CVI in the course of subthreshold yellow laser therapy.
Kaderli ST, Karalezli A, Kaderli A, Taskin SC, Sul S. Evaluation of the choroidal vascularity index after subthreshold yellow laser treatment in the patients with chronic central serous chorioretinopathy. Eye. Published online May 13, 2022. doi:10.1038/s41433-022-02090-7